1) Field of the Invention
The present invention relates to an arrangement for controlling the edge of pulp mass in a web former, the web former comprising a space formed by two wires or the like, into which space the pulp mass is fed, the wires being supported on chamber units, which each time include at least one chamber for receiving the water removed from the pulp mass, and in conjunction with the side edge of the said web former there being arranged pulp mass edge control means, for preventing the pulp mass edge from passing and/or spreading in the lateral direction of the web former into the area of the side edge of the web former, said edge control means including means for feeding pressurised injection water into the area of the side edge of the web former.
The invention also relates to a method for controlling the edge of pulp mass, in which method the pulp mass is fed into a space formed by two wires, the wires or the like being supported on chamber units, which each time include at least one chamber for receiving the water removed from the pulp mass, and in conjunction with the side edge of the said web former there being arranged pulp mass edge control means, for preventing the pulp mass edge from passing and/or spreading in the lateral direction of the web former into the area of the side edge of the web former, in which method pressurised injection water is fed into the area of the side edge of the web former.
2) Description of Related Art
The Applicant's earlier Finnish patent application 19982539 discloses an apparatus for forming a pulp web, which resembles the present invention in basic principle. The apparatus comprises a headbox from which pulp mass is fed into a narrowing, wedge-like space formed by two wires, in which the dry matter content of the mass is increased by removing water from the mass in a controlled manner into a chamber for receiving it. At the end of the narrowing space are compaction means, by which the dry matter content of the mass is further increased. The invention according to the application 19982539 thus relates mainly to a method and apparatus for controlling the dry matter content of the mass during web forming. In this case, therefore, the lateral spreading of the mass towards the side edges of the wires and the water chambers and past them has hardly been considered at all. In practice, this spreading has been prevented with edge bars connected to the side edges, the purpose of which is mainly to prevent the mass from spreading outside the web former.
The aim of the present invention is to eliminate or substantially reduce the disadvantages of the prior art and further to provide an improved solution for controlling the edges of pulp mass in a web former.